Dowel bar contraction joint



Jan. 26, 1943. ROBERTSON 2,309,538

DOWEL BAR CONTRACTION JOINT Filed July 19, 1941 Z EVE b; a;

7o%ez J5 er 60/2 Patented Jan. 26, 1943 UNITED STATES TENT ()FFICE 7 Claims.

This invention relates to concrete road joints, and more particularly to a road contraction joint of the dowel bar type in which a. plurality of dowel bar units are supported at spaced intervals on a base provided with a cracking fin or rib on which auxiliary cracking plates, carried by the dowel bar units are engaged, said auxiliary cracking plates being positioned between split load transmitting sleeves or collars carried on the dowel bars to be embedded in opposite road slabs which are separated by the joint crack produced by the contraction joint mechanisms.

It is an object of this invention to provide an improved form of road contraction joint of the dowel bar type, wherein the dowel bars carry both load transmitting members as Well as joint crack forming members.

Another object of the invention is the provision of a road contraction joint wherein spaced dowel bar units include pairs of split flanged load transmitting collars for embedding in the opposite road slabs separated by the joint to provide a means whereby loads or stresses applied to one of the road slabs may be transmitted through the joint to the opposite road slab to distribute the applied load or disseminate the stresses.

It is a further object of this invention to provide an improved type of road contraction joint of the dowel bar type wherein dowel bars are supported in spaced relationship on a base, with said dowel bars carrying spaced cracking plates the lower ends of which are formed to engage the base.

It is furthermore an object of this invention to provide a road contraction joint wherein dowel bars are supported in spaced parallel relationship upon a base with said dowel bars carrying cracking plates formed to engage the base and also serving as supports for an upper cracking member.

It is an important object of this invention to provide a road contraction joint of the dowel bar type wherein spaced dowelbar units are supported on a base which is formed with a lower cracking member positioned beneath an upper cracking member which in turn is supported by intermediate cracking members engaged with the lower cracking member. The intermediate cracking members are supported on the dowel bars between load transmitting split collars having split flanges contacting opposite sides of the intermediate cracking members, thereby providing a contraction joint which will not only properly crack and separate the road slabs but will cause stresses and loads applied to one of the road slabs to be transmitted through .the joint to the opposite road slab.

Other and further important objects of this invention will be apparent from the disclosures in the specification and the accompanying drawing.

The invention in a preferred form, is illustrated in the drawing and hereinafter more fully described.

In the drawing:

Figure 1 is a fragmentary isometric view of a dowel bar contraction joint mechanism embodying the principles of this invention.

Figure 2 is an enlarged fragmentary side elevational view of a portion of the joint mechanism looking at the end of a dowel bar unit.

Figure 3 is an enlarged fragmentary section across an expansion joint mechanism showing the concrete road slabs in position for embedding the joint mechanism and with parts of the slabs omitted to expose portions of the various members of the joint mechanism.

As shown in the drawing:

The present invention covers a contraction joint for concrete pavements with load transfer and pavements splitting dowel units forming a part thereof.

The contraction road joint forming mechanism comprises a metal base plate I adapted to be placed transversely on a road subgrade and extending from the center joint of the road to one edge thereof. The base plate I has the middle portion thereof formed to provide an upwardly projecting rib or fin 2 which extends longitudinally and centrally throughout the length of the base plate. The rib or fin 2 performs the function of a lower pavement cracking member, to coact with other cracking members hereinafter described for the purpose of transversely cracking the concrete of the pavement to form road slabs 3 and 4. The improved contraction joint forming mechanism includes a series of parallel spaced dowel bar units positioned transversely upon the base plate I. Each of the dowel bar units comprises a pair of dowel bar supporting brackets or holders provided with lugs at the bottom thereof for engaging through openings provided in the base plate I for holding the dowel bar brackets or holders in place.

Each of the dowel bar supporting brackets or holders is constructed of sheet metal stamped or cut in a developed form which is then bent into shape to provide a concave or substantially semi-cylindrical cradle or pocket 5 having upwardly projecting and inwardly curved gripping lugs or fingers 6 integrally formed thereon for the purpose of gripping around opposite sides of a dowel bar I. Integrally formed on opposite sides of the dowel bar supporting cradle 5 are channel-shaped supporting legs 8 which extend downwardly and outwardly from the cradle 5, preferably at an acute angle to one another, and have the lower ends thereof provided with integral toes or lugs 9 which project through slots or openings in the base plate I and are then bent over to engage against the bottom surface of said base plate as clearly illustrated in Figures 2 and 3.

As clearly illustrated in Figure 1 the two dowel bar supporting brackets or holders of each dowel bar unit, are mounted opposite one another upon the base plate I and on opposite sides of the fin or rib 2 in position to receive and support the ends of a dowel bar 5 seated in the cradles 5 and retained in place by means of the gripping lugs or fingers B.

Mounted centrally upon the dowel bar 7 is an intermediate or auxiliary cracking plate H) which is provided with an opening through which the dowel bar 1 projects. The lower end of the auxiliary cracking plate it is provided with a plurality of cuts or slits which divide the lower margin of the auxiliary crackiir plate into a plurality of gripping lugs or fingers H which alternately project downwardly on opposite sides of the base plate fin or rib 2 to hold the lower end of the auxiliary cracking plate It secured in position.

The upper marginal portion of each of the auxiliary cracking plates id is provided with an opening 12 for receiving an anchoring lug or finger !3 which is integrally formed on a lower margin of an upper cracking member of substantially U-shaped cross section comprising integrally connected side plates I4 and I5. The anchoring lugs 53 are formed on the lower margin of the side plate i while the opposite side rl i5 is provided with a longitudinally exng inwardly projecting stop head or rib l6 which is adapted to rest on the upper edges of the auxiliary cracking plates H), as clearly iliustrated in Figure 3, to hold the upper cracking member in position vertically above the lower cracking member 2 and serving as a connection between the intermediate or auxiliary cracking plates it of the joint mechanism.

Each of the dowel bar units is furthermore equipped with load transmitting mechanisms comprising a pair of split load transmitting sleeves or collars 11 each of which is provided with a radally split flange i3. The two flanged load transmitting sleeves or collars are reversed with respect to one another so that the flanges l8 thereof contact opposite surfaces of the crack plates S9 of the dowel bar units. It will thus be noted that each of the dowel bar units not only connects the opposite road slabs 3 and 4 to hold the same in proper position with respect to one another, but said dowel bar units also include both a cracking member and load transmitting members. The load transmitting members are arranged to transmit loads and stresses from one road slab through the joint to the opposite road slab and the flange members 58 of the load transmitting sleeves or collars ll abutting opposite sides of the auxiliary cracking plate I3 serves to brace the same in position.

Attention is called to the arrangement of the various cracking members namely the lower cracking member 2, the upper cracking member !4I5 and the upright auxiliary cracking memhere it) all of which are connected to form a cracking frame which extends upwardly from the base plate I to within a short distance of the top of the road. The space above the top cracking member and between the road slabs 3 and 4 may temporarily be filled with a removable top groove former which after the pouring of concrete and the partial setting of the concrete to form the road slabs, may be removed so that the space may be filled with asphaltum or pitch.

It will of course be understood that various details of construction may be varied through a wide range without departing from the principles of this invention, and it is, therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claims.

I claim as my invention:

1. A road joint dowel bar assembly comprising a base plate for seating on the road subgrade and having slots therein, a plurality of dowel bar holders, legs on said holders supported on the base plate and engaged in the slots thereof, dowel bars supported in the holders, cracking members supported on the dowel bars, gripping lugs integrally formed on the cracking members engaging the base plate to hold the cracking members in position, and flanged load transmitting members on the dowel bars with the flanges thereof in contact with opposite sides of the cracking members.

2. A road contraction joint dowel bar assembly comprising a base plate, a cracking frame supported longitudinally on the base plate and including upper and lower members connected by spaced plates, dowel bars projecting through the cracking frame plates, and flanged load transmitting collars mounted on the dowel bars with the flanges thereof in contact with opposite sides of the cracking frame plates.

3. A contraction joint dowel bar assembly comprising a base plate, a cracking member integrally formed longitudinally thereon, a plurality of auxiliary cracking members frictionally engaged at spaced intervals along the base plate crackfng member, dowel bars above the base plate and projecting through the auxiliary cracking members, and an upper cracking member connecting the upper ends of the auxiliary cracking members.

4. A road contraction joint dowel bar assembly comprising a base plate, a lower cracking member integrally formed centrally on the base plate, a plurality of auxiliary cracking members staggered gripping lugs thereon and engaged at spaced intervals with the lower cracking member, an upper cracking member connecting the upper ends of the auxiliary cracking members, dowel bars projecting through the auxiliary cracking members, and supports for the dowel bars secured to the base plate.

5. A road contraction joint dowel bar assembly comprising a base plate, a lower cracking member formed centrally along the length of the base plate, a plurality of auxiliary cracking members staggered gripping lugs thereon engaged on the lower cracking member, an upper cracking member supported on the auxiliary cracking members, dowel bars projecting through the auxiliary cracking members, supports for the dowel bars, split load transmitting members on the dowel bars on opposite sides of the auxiliary cracking members, and split flanges integral with the load transmitting members and contacting opposite sides of the auxiliary cracking members.

6. A road contraction joint assembly comprising a base, a plurality of cracking members clamped at spaced intervals on the base, dowel bars projecting through the cracking members, supports for the dowel bars on said base, and split flanged load transmitting members with the split flanges thereof contacting the dowel 10 bars on opposite sides of the cracking members.

ROBERT R. ROBERTSON. 

